Process for production of cresols

ABSTRACT

There is disclosed a process for the production of cresols, including the steps of: (a) conducting oxygenation of cymene with oxygen gas or an oxygen-containing gas, thereby obtaining a solution of oxygenation products containing tertiary and primary hydroperoxides of cymene; (b) reacting the solution of oxygenation products obtained in the step (a) with an organic quaternary ammonium salt and an alkali, or with an organic quaternary ammonium hydroxide, thereby decreasing the content of primary hydroperoxide; (c) subjecting the reaction mixture in the step (b) to decomposition in the presence of a catalyst; and (d) subjecting the decomposition mixture in the step (c) to hydrogenation, thereby obtaining the desired cresols.

CROSS REFERENCE

This application is a continuation of application Ser. No. 08/144,448filed on Nov. 2, 1993, now abandoned which is application Ser. No.08/045440, filed Apr. 20, 1993 now abandoned.

FIELD OF THE INVENTION

The present invention relates to a process for the production ofcresols.

BACKGROUND OF THE INVENTION

As a process for cresol production, there has been widely known aprocess in which cymene is oxygenated with oxygen gas and the resultingtertiary hydroperoxide of cymene is then decomposed into the desiredcresols and acetone.

In this process, however, a primary hydroperoxide of cymene with anoxygenated methyl group is formed as a by-product in the oxygenation,together with the above tertiary hydroperoxide. The primaryhydroperoxide is converted into isopropylphenol and formaldehyde throughits decomposition. This formaldehyde may be condensed with the resultingcresols to form a resin, which will cause a decrease in the yield ofcresols in this process.

To solve this problem, a process has been proposed, in which thedecomposition of the primary hydroperoxide is stopped halfway tosuppress the formation of formaldehyde, so that a yield decrease arisingfrom this by-product can be prevented, and the remaining primaryhydroperoxide is then hydrogenated into an alkylbenzene (see, e.g., JP-A52-57130, JP-B 59-8246, JP-B 1-49248).

In this process, however, a portion of the primary hydroperoxide stilldecomposes. Therefore, there will inevitably occur to a certain degreethe side reaction between formaldehyde as the by-product and cresols asthe major product, so that a loss of cresol yield will accompany theprocess. This process is not satisfactory with respect to the yield ofcresols.

For the purpose of preventing the formation of formaldehyde, a processhas been proposed, in which a mixture of the tertiary and primaryhydroperoxides obtained by the oxygenation is reacted with an alkali andan organic quaternary ammonium salt to reduce the content of primaryhydroperoxide (see, e.g., JP-A 63-35552). This process involves noformation of formaldehyde as a by-product in the production of cresols,so that any decrease in the yield of cresols arising from Theformaldehyde formation can be prevented; however, the primaryhydroperoxide is not effectively utilized in this process, and it cannotalways be said that this process is satisfactory from the viewpoint ofan improvement in the yield of cresols.

SUMMARY OF THE INVENTION

Under these circumstances, the present inventors have intensivelystudied a production process for cresols. As the result, they have founda novel process through a series of steps comprising: reacting, inadvance of decomposition, with an organic quaternary ammonium salt andan alkali, or with an organic quaternary ammonium hydroxide, a solutionof oxygenation products containing the tertiary and primaryhydroperoxides of cymene, which has been obtained by oxygenation ofcymene with oxygen gas or an oxygen-containing gas, so that the contentof primary hydroperoxide is decreased; subjecting the reaction mixtureto decomposition; and subjecting the decomposition mixture tohydrogenation, thereby obtaining cresols with high yield.

This process makes it possible to prevent any decrease in the yield ofcresols arising from the formation of formaldehyde by decomposition ofthe primary hydroperoxide which is usually seen in any conventionalprocess as described above, and also makes it possible to selectivelyrecover the decomposition products of the primary hydroperoxide andother by-products in the form of cymene as the raw material, therebyattaining an improvement in the yield of cresols.

That is, the present invention provides a process for the production ofcresols, comprising the steps of:

(a) conducting oxygenation of cymene with oxygen gas or anoxygen-containing gas, thereby obtaining a solution of oxygenationproducts containing tertiary and primary hydroperoxides of cymene; (b)reacting the solution of oxygenation products obtained in the step (a)with an organic quaternary ammonium salt and an alkali, or with anorganic quaternary ammonium hydroxide, thereby decreasing the content ofprimary hydroperoxide; (c) subjecting the reaction mixture in the step(b) to decomposition in the presence of a catalyst; and (d) subjectingthe decomposition mixture in the step (c) to hydrogenation, therebyobtaining the desired cresols.

DETAILED DESCRIPTION OF THE INVENTION

The following will describe the step of conducting the oxygenation ofcymene with oxygen gas or an oxygen-containing gas no obtain a solutionof oxygenation produces containing tertiary and primary hydroperoxidesof cymene.

The raw material, cymene, used in this step may be in various forms suchas o-cymene, m-cymene and p-cymene. The compounds of these forms can beused solely or in combination with each other at any proportion.

This seep can be performed by ordinary oxygenation in liquid phase, andusually attained by bringing cymene in contact with oxygen gas or anoxygen-containing gas such as air.

The oxygenation is usually conducted under normal pressure or underpressure. The pressure of oxygen gas or an oxygen-containing gas isusually in the range of from 0 to 20 kg/cm² as a gauge pressure.

In this step, an alkali may be allowed no coexist in the reactionsystem, examples of which are carbonates of alkali metals, such assodium carbonate and potassium carbonate; hydroxides of alkaline earthmetals, such as magnesium hydroxide and calcium hydroxide; carbonates ofalkaline earth metals, such as calcium carbonate; amines such aspyridine, piperidine and triethylamine; and ammonia. These alkalis maybe used in the form of a solution, if possible.

In this step, an initiator may be added co the reaction system, examplesof which are azo compounds such as 2,2'-azobisisobutyronitrile, andperoxides such as benzoyl peroxide and cymene hydroperoxide. The amountof initiator to be used is usually in the range of from 0.01% to 5% byweight, based on the weight of cymene.

The reaction temperature is usually in the range of from 30° to 200° C.,preferably from 80° to 150° C.

The ratio of formed primary hydroperoxide to formed tertiaryhydroperoxide is usually in the range of from 5-30/95-70(primary/tertiary; the sum total of both is 100).

After completion of the reaction, a solution of oxygenation products isobtained, which may be further subjected, if necessary, to an ordinarypost-treatment such as fractionation with a separatory funnel orfiltration. This solution of oxygenation products can be used in thesubsequent step without undergoing a particular post-treatment; in casewhere no alkali is used in this step, however, the resulting solution ofoxygenation products may be washed, before its use in the subsequentstep, with an aqueous solution of alkali substances such as hydroxidesof alkali metals, carbonates of alkali metals, hydroxides of alkalineearth metals or carbonates of alkaline earth metals.

The following will describe the step of reacting the solution ofoxygenation products obtained in the foregoing step with an organicquaternary ammonium salt and an alkali, or with an organic quaternaryammonium hydroxide, thereby decreasing the content of primaryhydroperoxide.

Examples of the organic quaternary ammonium salt which can be used inthis reaction are a compound of the general formula: ##STR1## wherein R¹and R² are independently a C₁ -C₂₄ alkyl group or an aralkyl group, bothof which are optionally substituted with at least one substituent; R³and R⁴ are independently a C₁ -C₁₀ alkyl group; and X is an anionreside; and a compound of the general formula: ##STR2## wherein R⁵ is anoptionally substituted C₁ -C₂₄ alkyl group; R⁶ is a hydrogen atom or aC₁ -C₂ alkyl group; and X is the same as defined above.

In both compounds as shown above, examples of the anion residue arehalogen atoms such as chlorine, bromine and iodine; and acid residuessuch as H₂ PO₄, CH₃ COO, CH₃ OSO₃, C₂ H₅ OSO₃, ClO₄ and HSO₄.

As the optionally substituted aralkyl group in the compound [1], therecan be exemplified benzyl, 1-phenethyl and 2-phenethyl, all of which maybe substituted in any way.

Typical examples of the compounds [1] and [2] are tetramethylammoniumchloride, tetraethylammonium chloride, tetra-n-propylammonium chloride,tetra-n-butylammonium chloride, benzyltrimethylammonium chloride,benzyltriethylammonium chloride, stearyltrimethylammonium chloride,trimethyloctadecylammonium chloride, lauryltrimethylammonium chloride,trimethylhexadecylammonium chloride, distearyldimethylammonium chloride,dicetyldimethylammonium chloride, tricaprylmethylammonium chloride, o-,m- and p-methoxybenzyltriethylammonium chlorides, o-, m- andp-phenoxybenzyltriethylammonium chlorides, trimethyldodecylammoniumchloride, trimethyldecylammonium chloride, triocrioctylmethylammoniumchloride, N-butylpyridinium chloride, N-laurylpyridinium chloride,N-laurylpicolinium chloride, triethylpropylammonium chloride,diethylpropylbenzylammonium chloride, o-, m- andp-chlorobenzyltriethylammonium chlorides,methylethylpropylbenzylammonium chloride, diethylbutylbenzylammoniumchloride, methyldiethylbenzylammonium chloride,dimethylethylbenzylammonium chloride, tripropylbenzylammonium chloride,ethyldipropylbenzylammonium chloride, diethyldibenzylammonium chloride,dimethyllaurylbenzylammonium chloride, dimethylstearylbenzylammoniumchloride, dimethyloctylbenzylammonium chloride,dimethylmyristylbenzylammoium chloride, as well as bromides, iodides,perchlorates, dihydrogenphosphates, hydrogensulfates, methylsulfates andethylsulfates corresponding to these chlorides. These compounds can beused solely or in admixture with each other. The amount of thesecompound to be used is usually in the range of from 0.001 to 1 mole,preferably from 0.001 to 0.5 moles, per mole of the primaryhydroperoxide.

Examples of the alkali which can be used together with the organicquaternary ammonium salt are hydroxides of alkali metals and hydroxidesof alkaline earth metals, such as sodium hydroxide, potassium hydroxide,lithium hydroxide, calcium hydroxide, barium hydroxide, magnesiumhydroxide and strontium hydroxide. The amount of alkali to be used isusually in the range of from 0.1 to 20 moles, preferably from 0.5 to 10moles, per mole of the primary hydroperoxide.

In case where an organic quaternary ammonium hydroxide is used in theabove reaction, it is possible to use a compound of the general formula:##STR3## wherein R⁷ and R⁸ are independently a C₁ -C₂₄ alkyl group or anaralkyl group, both of which are optionally substituted with at leastone substituent; R⁹ and R¹⁰ are independently a C₁ -C₁₀ alkyl group; ora compound of the general formula: ##STR4## wherein R¹¹ is an optionallysubstituted C₁ -C₂₄ alkyl group; R¹² is a hydrogen atom or a C₁ -C₂alkyl group.

As the optionally substituted aralkyl group in the compound [3], therecan be exemplified benzyl, 1-phenethyl and 2-phenethyl, all of which maybe substituted in any way.

Typical examples of the compounds [3] and [4] are tetramethylammoniumhydroxide, tetraethylammonium hydroxide, tetra-n-propylammoniumhydroxide, tetra-n-butylammonium hydroxide, benzyltrimethylammoniumhydroxide, benzyltriethylammonium hydroxide, stearyltrimethylammoniumhydroxide, trimethyloctadecylammonium hydroxide, lauryltrimethylammoniumhydroxide, trimethylhexadecylammonium hydroxide,distearyldimethylammonium hydroxide, dicetyldimethylammonium hydroxide,tricaprylmethylammonium hydroxide, o-, m- andp-methoxybenzyltriethylammonium hydroxides, o-, m- andp-phenoxybenzyltriethylammonium hydroxides, trimethyldodecylammoniumhydroxide, trimethyldecylammonium hydroxide, trioctylmethylammoniumhydroxide, N-butylpyridinium hydroxide, N-laurylpyridinium hydroxide,N-laurylpicolinium hydroxide, triethylpropylammonium hydroxide,diethylpropylbenzylammonium hydroxide, o-, m- andp-chlorobenzyltriethylammonium hydroxides,methylethylpropylbenzylammonium hydroxide, diethylbutylbenzylammoniumhydroxide, methyldiethylbenzylammonium hydroxide,dimethylethylbenzylammonium hydroxide, tripropylbenzylammoniumhydroxide, ethyldipropylbenzylammonium hydroxide,diethyldibenzylammonium hydroxide, dimethyllaurylbenzylammoniumhydroxide, dimethylstearylbenzylammonium hydroxide,dimethyloctylbenzylammonium hydroxide and dimethylmyristylbenzylammoiumhydroxide. These hydroxides can be used solely or in admixture with eachother. The amount of these hydroxides to be used is usually in the rangeof from 0.001 to 5 moles, per mole of the primary hydroperoxide.

In case where an organic quaternary ammonium hydroxide is used, it ispreferred to combine an alkali therewith, because the amount of organicquaternary ammonium hydroxide to be used can be decreased. The amount oforganic quaternary ammonium hydroxide to be used in this case is usuallyin the range of from 0.001 to 1 mole, preferably 0.001 to 0.5 moles, permole of the primary hydroperoxide. The amount of organic quaternaryammonium hydroxide to be used with no alkali is usually in the range offrom 0.1 to 5 moles, preferably 0.3 to 3 moles, per mole of the primaryhydroperoxide.

Examples of the alkali which can be used together with the organicquaternary ammonium hydroxide are hydroxides of alkali metals andhydroxides of alkaline earth metals, such as sodium hydroxide, potassiumhydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide,magnesium hydroxide and strontium hydroxide. The amount of alkali to beused is usually in the range of from 0.1 to 20 moles, preferably from0.5 to 10 moles, per mole of the primary hydroperoxide.

The reaction in this step is usually conducted in the presence of apolar solvent such as water, methanol or ethanol. Preferably used iswater.

The reaction temperature is usually in the range of from 30° C, to 150°C., preferably from 70° C. to 110° C.

By this selective decomposition, the primary hydroperoxide isselectively decomposed, so that formaldehyde cannot be formed as aby-product in the subsequent decomposition step for obtaining thedesired cresols. Accordingly, there is no possibility that the yield ofcresols may be decreased by the side reaction between the resultingcresols and the formaldehyde. Further, by the additional hydrogenationof the reaction mixture after the decomposition of the tertiaryhydroperoxide into the cresols, the decomposition products from theprimary hydroperoxide and other by-products are converted into the rawmaterial cymene which will be recycled, resulting in an increase in theyield of cresols from the consumed cymene.

While the decomposition reaction is selective, the tertiaryhydroperoxide can also be reacted, together with the primaryhydroperoxide. The reaction rate of the tertiary hydroperoxide isconsiderably lower than that of the primary hydroperoxide, and thedecomposition products from the tertiary hydroperoxide can be recoveredin the form of cymene by hydrogenation after the decomposition of thetertiary hydroperoxide into cresols; therefore, the final yield ofcresols from consumed cymene becomes higher than that attained by anyconventional process. It is, however, disadvantageous from an economicalpoint of view that the tertiary hydroperoxide is decomposed to a degreethan required. It is usually advantageous from an economical point ofview, i.e., the yield of cresols through one pass and the energyefficiency in the process, that the decomposition is conducted so thatthe weight ratio of primary hydroperoxide to tertiary hydroperoxide isusually decreased to not greater than 1/25 (w/w), preferably not greaterthan 1/50 (w/w), more preferably not greater than 1/100 (w/w), whichmakes it possible to decrease the formation of by-products responsiblefor any yield decrease in the subsequent step, and that the degree ofconversion of tertiary hydroperoxide as the precursor of cresols issuppressed to become 20% or less, preferably 10% or less, morepreferably 5% or less.

These results of decomposition can be attained by adjusting theconcentration of alkali, the amount of organic quaternary ammonium saltor hydroxide to be used, and the reaction temperature, to the aboveprescribed values.

In this step, the reaction mixture may be subjected to an analysis suchas liquid chromatography to check the weight ratio of primaryhydroperoxide to tertiary hydroperoxide, which also makes it possible todetermine the end point of the reaction.

After completion of the reaction, for example, the reaction mixture maybe allowed to stand and subjected to fractionation with a separatoryfunnel, followed by washing with water, before its use in the subsequentstep.

The following will describe the step of subjecting the reaction mixtureobtained in the foregoing step to decomposition in the presence of acatalyst.

Examples of the catalyst which can be used in this step are acidiccatalysts, sulfur and Burman catalysts. Specific examples of the acidiccatalyst are inorganic acids such as sulfuric acid, hydrochloric acid,perchloric acid, SO₂ and SO₃ ; organic acids such as benzenesulfonicacid, p-toluenesulfonic acid, cresolsulfonic acid and chloroacetic acid;solid acids such as silica-alumina, alumina and acidic ion exchangeresin; heteropolyacids such as tungstosilicic acid, tungstophosphoricacid and molybdophosphoric acid. The Burmah catalyst refers to acatalyst carrying a metal complex of the general formula: ##STR5##wherein M is Ni, Pd or Fe(II); Ph is a phenyl group optionallysubstituted with at least one substituent; n is an integer of 1, 2 or 3;z is a formal charge of the complex, selected from 0, -1 and -2.Examples of the Burmah catalyst are bis(dithiobenzil)nickel,bis(dithiobenzil)palladium and bis(dithiobenzil)iron(II). Preferredcatalysts are sulfuric acid and cresolsulfonic acid. The amount ofcatalyst to be used, although it can be determined depending upon thekind of that catalyst, is usually in the range of from about 0.0001% to1% by weight, based on the weight of the reaction mixture to be treated.

The reaction temperature is usually in the range of from 30° to 150° C.

In this step, the mixture thus treated may be subjected to an analysissuch as liquid chromatography to check the degree of decomposition ofhydroperoxides.

After completion of the reaction, the reaction mixture can be used inthe subsequent seep without under-going a particular post-treatment, orif necessary, after subjected to a post-treatment such as filtration andneutralization. Alternatively, the reaction mixture can also be used inthe subsequent step after the removal of acetone produced.

The following will describe the step of subjecting the decompositionmixture obtained in the foregoing seep to hydrogenation.

This step can be performed by ordinary catalytic hydrogenation, andusually attained by introducing hydrogen gas in the reaction systemunder normal pressure or under pressure in the presence of a catalyst.The pressure of hydrogen gas is usually in the range of from 0 to 100kg/cm² as a gauge pressure.

Examples of the catalyst which can be used in this step are thosecomposed of a metal such as Pd, Cr, Cu, Pt, Ni, Ru, Rh or Re. Thesecatalysts can also be used in a supported form on a carrier such asactive carbon, titania, zirconia, silica-magnesia, alumina-magnesia,alumina or acidic ion exchange resin. Preferred are those composed of Pdor Cu--Cr. More preferred are Pd/C, Pd/alumina, Pd/TiO₂, Cu--Cr/C,Cu--Cr/TiO₂ and Pd/acidic ion exchange resin. The amount of catalyst tobe used is usually in the range of from 0.001% to 20% by weight, basedon the weight of the decomposition mixture to be treated.

In this step, any other catalyst may be allowed to coexist in thereaction system, if necessary. Examples of such a catalyst are. the samecatalysts as used in the decomposition step. The decompostion mixturemay be used as it is, without undergoing the removal of the catalystused in the decomposition step.

The reaction temperature is usually in the range of from 0° to 250° C.,preferably from 20° to 250° C.

After completion of the reaction, the removal of the catalyst byfiltration gives cresols, cymene and acetone, which can be separated andpurified, if necessary, by neutralization and then distillation.

The by-products formed by the selective decomposition of the primaryhydroperoxide in the foregoing step can be converted into cymene andthen recovered, together with the unreacted portion of cymene, bothbeing recycled as the raw material in the process of the presentinvention.

The process of the present invention comprising the aforesaid steps isquite different from any conventional process in that any decrease inthe yield of cresols arising from their reaction with the by-productformaldehyde can be prevented and the by-products formed by oxygenationof cymene can effectively be recovered in the form of cymene, therebyattaining an improvement in the yield of cresols from consumed cymene,as compared with that obtained by any conventional process.

The process of the present invention can be performed either by a batchor a continuous method.

According to the process of the present invention, cresols can beobtained in high yield by conducting oxygenation of cymene with oxygengas or an oxygen-containing gas, followed by treatment with an organicquaternary ammonium salt and an alkali, or with an organic quaternaryammonium hydroxide, thereby decreasing the content of primaryhydroperoxide, and further by subjecting the reaction mixture todecomposition and then hydrogenation, thereby preventing the sidereaction responsible for any yield decrease and effectively recoveringthe by-products in the form of cymene. The process of the presentinvention has an additional advantage that the resulting cresols canreadily be isolated from the by-products.

The present invention will be further illustrated by way of thefollowing examples which are not to be construed to limit the scopethereof.

The following abbreviated names are used in the Examples with referenceto the compounds of the respective structures as shown below. ##STR6##

EXAMPLE 1

I. In a reaction vessel equipped with a stirrer, an air-blowing tube, athermometer and a condenser, placed is raw material cymene (5045 partsby weight; composition: cymene, 98.3%; 3HPO, 1.10%; 1HPO, 0.032%; CAL,0.122%; CUL, 0.007%; CUA, 0.0540%; CLF, 0.007%) containing cymenehydroperoxide (1.13%) as a reaction initiator. The reaction isconducted, while blowing air thereinto, at 120° C. under normal pressurefor 6 hours. After completion of the reaction, 5116 parts by weight of asolution of oxygenation products (composition: cymene, 86.2%; 3HPO,9.28%; 1HPO, 1.68%; CAL, 0.620%; CUL, 0.073%; CUA, 0.125%; CLF, 0.006%)is obtained.

II. The solution of oxygenation products (500 parts by weight) obtainedin Sec. I. of this Example is placed in a reaction vessel, to whichbenzyltriethylammonium chloride (0.507 parts by weight) and 8% aqueoussodium hydroxide (49.5 parts by weight) are added, and the mixture isstirred at 80° C. for 2.5 hours. The mixture is allowed to stand and thewater phase is removed therefrom with a separatory funnel to give 498parts by weight of the organic phase (composition: cymene, 86.3%; 3HPO,9.22%; 1HPO, 0.005%; CAL, 0.953%; CUL, 0.114%; CUA, 1.69%; CLF, 0.001%).The weight ratio of 1HPO to 3HPO in the organic phase is 1/1844, and thedegree of conversion is 99.7% for 1HPO and 0.972% for 3HPO,respectively.

To a reaction vessel charged with one portion of the resulting organicphase (488 parts by weight), added is water (50.0 parts by weight.), andthe mixture is stirred for washing at 80° C. for 1 hour. Then, themixture is allowed to stand and the water phase is removed therefromwith a separatory funnel to give 487 parts by weight of the washedorganic phase (composition: cymene, 86.4%; 3HPO, 9.36%; 1HPO, 0.007%;CAL, 0.984%; CUL, 0.130%; CUA, 1.67%; CLF, 0.001%).

One portion of the resulting washed organic phase (477 parts by weight)is condensed at 70° C. under reduced pressure (10 to 20 mmHg) to recover391 parts by weight of cymene (cymene content, 98.7%) as a distillateand to give 83.9 parts by weight of condensed oil (composition: cymene,30.5%; 3HPO, 51.9%; 1HPO, 0.0710%; CAL, 5.46%; CUL, 0.620%; CUA, 9.17%;CLF, not found) as a bottom residue.

III. The concentrated oil (20.0 parts by weight) obtained in Sec. II ofthis Example is added to a mixture of sulfuric acid (0.00803 parts byweight) and acetone (2.01 parts by weight) under reflux with stirring.After completion of the addition, the mixture is maintained at 65° C.for 15 minutes to give 21.7 parts by weight of the decomposition mixture(composition: cymene, 28.4%; 3HPO, not found; 1HPO, not found; CAL,0.417%; CUL, 1.57%; CUA, 7.31%; CLF, 30.0%; DMST, 3.00%; others, 29.3%).The degree of conversion of 3HPO is 100% and the yield of CLF is 96.6%(from 3HPO before the acid decomposition). The total yield of cresolfrom the oxygenation step to this step is 58.8%.

IV. In an autoclave made of stainless steel, placed are thedecomposition mixture (15.0 parts by weight) obtained in Sec. III. ofthis Example, 5% palladium-titania catalyst (0.300 parts by weight) andacidic ion exchange resin (Rohm & Haas Co.; trade name, Amberlyst 15;0.294 parts by weight). The hydrogenation is conducted, whileintroducing hydrogen gas thereinto under a hydrogen gauge pressure of 5kg/cm², at 40° C. for 2 hours and then at 75° C. for 1 hour. Aftercompletion of the reaction, the catalyst is removed by filtration, and.the reaction mixture is neutralized by addition of aqueous sodiumhydroxide until the water phase has pH 7. The reaction mixture isallowed to stand and the water phase is removed therefrom with aseparatory funnel to give 15.0 parts by weight of the reaction mixture(composition: cymene, 42.8%; 3HPO, not found; 1HPO, not found; CAL,0.0730%; CUL, 0.161%; CUA, not found; CLF, 30.7%; DMST, 0.363%; others,25.9%). The total yield of cresol is 78.2% (from consumed cymene).

The degree of conversion of by-products (CAL+DMST+CUA+CUL) in thisreduction step is 95.0%, the yield of cymene is 126.1% (from by-products(CAL+DMST+CUA+CUL) before the hydrogenation), and the recovery-of cresolis 102.3% (to the amount of cresol before the hydrogenation).

EXAMPLES 2-10

The oxygenation mixture obtained in Sec. I of Example 1 is used for thetreatment of a hydroperoxide mixture with an organic quaternary ammoniumsalt or hydroxide in the same manner as described in Sec. II of Example1, except for the conditions shown in Table 1. The results are shown inTable 1.

                                      TABLE 1                                     __________________________________________________________________________    Organic quaternary ammonium              1HPO/3HPO in                         salt or hydroxide     Mole ratio                                                                          Reaction                                                                           1HPO                                                                              3HPO                                                                              oil phase after                      Example         Mole ratio                                                                          of alkali                                                                           time conv.                                                                             conv.                                                                             reaction                             No.  Kind       (to 1HPO)                                                                           (to 1HPO)                                                                           (hr) (%) (%) (weight ratio)                       __________________________________________________________________________    2    Benzyltriethyl-                                                                          0.039 1.66  2.0  98.9                                                                              1.6 1/494                                     ammonium hydroxide                                                       3    Benzyltriethyl-                                                                          0.49  2.08  0.17 100 1.0 --                                        ammonium hydroxide                                                       4    Lauryltrimethyl-                                                                         0.042 2.10  2.0  99.2                                                                              0.3 1/688                                     ammonium chloride                                                        5    Cetyltrimethyl-                                                                          0.040 2.50  2.0  99.4                                                                              1.0 1/911                                     ammonium chloride                                                        6    Stearyltrimethyl-                                                                        0.031 2.10  2.0  99.3                                                                              2.2 1/772                                     ammonium chloride                                                        7    Benzyltriethyl-                                                                          0.11  2.52  1.33 95.3                                                                              2.1 1/115                                     ammonium chloride                                                        8    Lauryltrimethyl-                                                                         0.11  2.10  1.17 95.6                                                                              1.6 1/124                                     ammonium chloride                                                        9    Benzyltriethyl-                                                                          1.1   0     2.0  100 2.0 --                                        ammonium hydroxide                                                       10   Tetramethyl-                                                                             2.6   0     2.0  100 0   --                                        ammonium hydroxide                                                       __________________________________________________________________________

The reaction mixture obtained in the foregoing step is washed with waterand concentrated, after which the subsequent steps are conducted in thesame manner as described in Secs. III-IV of Example 1, thereby obtainingthe desired cresols and cymene with high yield.

EXAMPLE 11

The oxygenated oil (250 parts by weight; composition: cymene, 85.2%;3HPO, 9.84%; 1HPO, 1.58%; CAL, 0.873%; CUL, 0.142%; CUA, 0.153%; CLF,0.015%) obtained in Sec. I of Example 1 is stirred together with 4%aqueous sodium hydroxide (25.0 parts by weight) under an atmosphere ofnitrogen at 70° C. for 0.25 hours to give 250 parts by weight ofneutralized oil (composition: cymene, 85.2%; 3HPO, 9.77%; 1HPO, 1.39%;CAL, 0.909%; CUL, 0.220%; CUA, 0.233%; CLF, 0.003%).

This neutralized oil (200 parts by weight) is placed in a reactionvessel, to which 8% aqueous sodium hydroxide (19.9 parts by weight) andbenzyltriethyl ammonium chloride (0.599 parts by weight) are added, andthe mixture is stirred under an atmosphere of nitrogen at 70° C. for0.25 hours. The reaction mixture is allowed to stand and the water phaseis removed with a separatory funnel to give 200 parts by weight oforganic phase (composition: cymene, 85.2%; 3HPO, 9.57%; 1HPO, 0.052%;CAL, 1.06%; CUL, 0.317%; CUA, 1.76%; CLF, 0.003%).

The weight ratio of 1HPO to 3HPO in the organic phase is 1/185, and thedegree of conversion is 96.3% for 1HPO and 2.03% for 3HPO, respectively.

EXAMPLES 12-21

The decomposition mixture obtained in Secs. I-III of Example 1 issubjected to hydrogenation in the same manner as described in Sec. IV ofExample 1, except for the conditions shown in Table 2. The results areshown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Catalyst          Acid additive                                                            Amount     Amount                                                             (based on  (based on    [A]*.sup.1                                                                        CYM*.sup.2                                                                         CLF*.sup.3                      Example      decomp.    decomp.                                                                             Temp. (°C.)                                                                   conv.                                                                             yield                                                                              reco.                                                                             Other                       No.  Kind    mixture)                                                                           Kind  mixture)                                                                            Time (hr)                                                                            (%) (%)  (%) conds.                      __________________________________________________________________________    12   5% Pd/TiO.sub.2                                                                       1 wt %                                                                             Amber- lyst 15                                                                      1 wt %                                                                               ##STR7##                                                                            96.7                                                                              126.8                                                                              101.4                           13   5% Pd/TiO.sub.2                                                                       1 wt %                                                                             Amber- lyst 15                                                                      2.5 wt %                                                                             ##STR8##                                                                            82.7                                                                              121.8                                                                              102.6                                                                             *4                          14   5% Pd/TiO.sub.2                                                                       1 wt %                                                                             98% H.sub.2 SO.sub.4                                                                0.08 wt %                                                                            ##STR9##                                                                            52.6                                                                              114.8                                                                              100.5                           15   5% Pd/TiO.sub.2                                                                       1 wt %                                                                             98% H.sub.2 SO.sub.4                                                                0.2 wt %                                                                             ##STR10##                                                                           75.8                                                                              142.5                                                                              101.3                           16   5% Pd/TiO.sub.2                                                                       1 wt %                                                                             Tungsto- silicic acid                                                               0.5 wt %                                                                             ##STR11##                                                                           83.5                                                                              149.7                                                                              100.4                           17   5% Pd/TiO.sub.2                                                                       1 wt %                                                                             Tungsto- phosphor- ic acid                                                          0.5 wt %                                                                             ##STR12##                                                                           62.4                                                                              124.0                                                                              98.3                            18   5% Pd/Al.sub.2 O.sub.3                                                                1 wt %                                                                             Amber- lyst 15                                                                      2.5 wt %                                                                             ##STR13##                                                                           94.9                                                                              168.7                                                                              102.1                           19   5% Pd/TiO.sub.2                                                                       1 wt %                                                                             None  --                                                                                   ##STR14##                                                                           86.2                                                                              103.4                                                                              99.7                            20   5% Pd/TiO.sub.2                                                                       1 wt %                                                                             None  --                                                                                   ##STR15##                                                                           78.5                                                                              104.2                                                                              96.8                            21   2% Pd/IER*.sup.5                                                                      2.5 wt %                                                                           None  --                                                                                   ##STR16##                                                                           47.6                                                                              110.3                                                                              105.1                           __________________________________________________________________________     *.sup.1 Total conversion of byproducts (CAL, DMST, CUA and CUL) in the        hydrogenation. [A] = CAL + DMST + CUA + CUL                                   ##STR17##                                                                     *.sup.2 Yield of CYM in the hydrogenation.                                    ##STR18##                                                                     *.sup.3 Recovery of CLF in the hydrogenation.                                 ##STR19##                                                                     *.sup.4 The decomposition mixture is subjected to neutralization before       hydrogenation.                                                                *.sup.5 Acidic ion exchange resin.                                       

What is claimed is:
 1. A process for the production of cresols,comprising the steps of:(a) oxygenating cymene with oxygen gas or anoxygen-containing gas in the absence of an alkali, to thereby obtain asolution of oxygenation products containing tertiary and primaryhydroperoxides of cymene; (b) carrying out a selective decompositionreaction on the oxygenation products obtained in the step (a) under anatmosphere of nitrogen with either:(i) an organic quaternary ammoniumsalt and an alkali, or (ii) an organic quaternary ammonium hydroxide, inthe presence or absence of alkali to thereby selectively decrease saidprimary hydroperoxides in the solution; (c) subjecting the resultantsolution from step (b) to decomposition in the presence of an acidiccatalyst, or sulfur or a Burmah catalyst; and (d) subjecting theresultant solution from step (c) to hydrogenation, subsequentlyseparating and recovering the desired cresols.
 2. A process according toclaim 1, wherein the reaction in the step (b) is conducted so that theweight ratio of remaining primary hydroperoxide to tertiaryhydroperoxide is decreased to not greater than 1/25 (w/w).
 3. A processaccording to claim 2, wherein a degree of conversion of tertiaryhydroperoxide in the step (b) is 20% or less.
 4. A process according toclaim 1, wherein the reaction in the step (b) is conducted with theorganic quaternary ammonium salt and the alkali.
 5. A process accordingto claim 2, wherein the reaction in the step (b) is conducted with saidorganic quaternary salt and said alkali.
 6. A process according to claim3, wherein the reaction in the step (b) is conducted with said organicquaternary ammonium salt and said alkali.
 7. A process according toclaim 1, wherein the reaction in the step (b) is conducted with saidorganic quaternary ammonium hydroxide and said alkali.
 8. A processaccording to claim 2, wherein the reaction in the step (b) is conductedwith said organic quaternary ammonium hydroxide and said alkali.
 9. Aprocess according to claim 3, wherein the reaction in the step (b) isconducted with said organic quaternary ammonium hydroxide and saidalkali.
 10. A process according to claim 1, wherein the hydrogenation inthe step (d) is conducted with a Pd catalyst or a Cu--Cr catalyst.
 11. Aprocess according to claim 2, wherein the hydrogenation in the step (d)is conducted with a Pd catalyst or a Cu--Cr catalyst.
 12. A processaccording to claim 3, wherein the hydrogenation in the step (d) isconducted with a Pd catalyst or a Cu--Cr catalyst.
 13. A processaccording to claim 4, wherein the hydrogenation in the step (d) isconducted with a Pd catalyst or a Cu--Cr catalyst.
 14. A processaccording to claim 5, wherein the hydrogenation in the step (d) isconducted with a Pd catalyst or a Cu--Cr catalyst.
 15. A processaccording to claim 6, wherein the hydrogenation in the step (d) isconducted with a Pd catalyst or a Cu--Cr catalyst.
 16. A processaccording to claim 7, wherein the hydrogenation in the step (d) isconducted with a Pd catalyst or a Cu--Cr catalyst.
 17. A processaccording to claim 8, wherein the hydrogenation in the step (d) isconducted with a Pd catalyst or a Cu--Cr catalyst.
 18. A processaccording to claim 9, wherein the hydrogenation in the step (d) isconducted with a Pd catalyst or a Cu--Cr catalyst.
 19. The processaccording to claim 1, wherein steps (a)-(d) in the process are carriedout sequentially.
 20. A process according to claim 1, wherein theprocess is carried out as a batch or a continuous method.
 21. Theprocess of claim 1, wherein said Burmah catalyst is a catalyst of thefollowing formula: ##STR20## wherein M is Ni, Pd or Fe (II); Ph is aphenyl group optionally substituted with at least one substituent; n isan integer of 1, 2 or 3; z is a formal charge of the complex, selectedfrom 0, -1 and -2.
 22. The process of claim 1, wherein subsequent to thestep (d) hydrogenation reaction, cymenes in said solution are recycledin said process.